The present invention relates to an apparatus for processing solid materials by burning, gasifying, calcining or retorting, and more particularly to an improved apparatus for retorting oil shale to recover oil therefrom having a gas distributor system for delivering and distributing thereto gas used in the shale processing. For simplicity, the processes hereinafter described will be referred to as "retorting" processes, and the vessels in which retorting is performed as "retorts" or "kilns ".
One example of solid materials processing in which the present invention finds particular use is in the recovery of oil from oil shale. Oil is recovered from oil shale by heating the shale to its destructive distillation (pyrolysis) temperature. Oil shale contains a high molecular weight organic material known as kerogen. At the destructive distillation temperature, the kerogen in the shale is destructively distilled to produce primarily lower molecular weight organic compounds which are referred to hereinafter as oil and oil vapor. Also produced, are noncondensable organic gases and a solid carbonaceous solid residue ("char"). The oil vapor produced mixes with hot gases from the heating process, then is cooled to condense to a mist, and the mixed gases and oil mist are further processed to recover the oil. It will be appreciated that the efficiency of the destructive distillation process, i.e., the percentage of the total oil capable being produced from the shale that is actually removed and recovered, is critical because it directly affects the cost of the resulting oil.
One type of relatively successful retorting process utilizes combustion (or oxidation) in a kiln containing the shale to develop the heat for the destructive distillation of the shale. This process is referred to as a direct heated process and has met with some success. See U.S. Pat. No. 4,042,485. Another relatively successful process, an indirect heated process, uses externally heated recycle gas to provide the heat for the destructive distillation process. See U.S. Pat. No. 4,116,810. In either case, it is important that the efficiency of the process be maximized. In addition, it is important that the cost of the process be minimized in order to keep down the cost of the recovered oil.
In both the indirect and direct heated methods, it is important that the processing gas be distributed substantially uniformly throughout the cross section of the retort for uniform heating and processing of the shale particles. This is required even though non-uniform conditions may exist in the retort, e.g., different grades of shale materials delivered to the several zones of the retort. Shale grade variations could be in kerogen content, carbonate amount and composition or particle size distribution.
Furthermore, it is important that the shale particles be disturbed as they descend through the retort to expose maximum surface area thereof to heating and to enhance controlled gas to solids content. It is also important that the means for delivering the processing gas be constructed to prevent potentially damaging heat concentration, and to withstand the weight of the descending oil shale bed as well as the high temperatures and other adverse conditions arising in the destructive distillation process.
Another example of solid materials processing in which the present invention is useful is in pyroprocessing of particulate solid materials such as the calcination of limestone. This process generally is a heat treatment of a raw material to produce a chemical change in the material. For example, various carbonates decompose under heat leaving the corresponding oxide, i.e., calcium oxide in lump form, and gaseous carbon dioxide. While each calcining process is dependent upon the material being treated, there are some common general principles which apply when certain types of equipment are used for the process. Thus, the present invention is applicable to calcining generally in vertical retorts, normally referred to as shaft furnaces, vertical kilns, etc. See U.S. Pat. No. 3,743,697.
Various other mineral ores, green petroleum coke in pellet or granular form, and other matter can be subjected to heat treatment in a vertical retort in accordance with the invention.